Abstract
The use of fly ash for the production of cement is a typical example of the utilization of by-products (waste) from various fields of production in construction, a significant reduction of CO2 emissions and reduction of energy consumption. However, in order to be able to determine the suitability of this additive in construction, it is necessary to examine the durability of cement composites with fly ash in various, often complicated, destructive environments. There are known publications regarding the durability of concretes with fly ash in individual environments. However, in natural conditions, several destructive environments are common at the same time. The article presents an attempt to reproduce natural conditions. This paper presents the results of sulphate expansion tests of air-entrained (AE) and non-air-entrained (nAE) Portland and fly ash cement mortars subjected to prior freezing and thawing. Despite significant strains experienced during freeze-thaw cycles, unlike the non-air-entrained Portland cement mortars, the non-air-entrained mortars made of fly ash cement did not exhibit any significant expansion when exposed to Na2SO4. For 17 months no expansion was found in the air-entrained mortars made of either of the cement types when immersed in Na2SO4solution after freezethaw cycles. The results of the SEM and EDS analyses showed that gypsum and ettringite were the sulphate attack products in all the mortars. The highest amounts of ettringite were found in air voids.
Highlights
Bearing in mind the climatic conditions in Poland and the scale of use of multicomponent cements, it seems relevant to investigate the interaction of frost damage and sulphate attack on the durability of air-entrained and non-air entrained cement composites from various cements
The lower temperature slowed down the diffusion of sulphate ions, which led to the slowing of sulphate attack
The aim of this study was to investigate the effects of the fly ash on durability of cement mortars exposed to complex deterioration conditions
Summary
Bearing in mind the climatic conditions in Poland and the scale of use of multicomponent cements, it seems relevant to investigate the interaction of frost damage and sulphate attack on the durability of air-entrained and non-air entrained cement composites from various cements. The durability of cementitious composites is defined as the degree of resistance to cyclic freeze-thawing, penetration, carbonation, stresses, and the action of chemical agents, for example, sulphate attack. Despite extensive knowledge on the sulphate attack of concrete, there have been cases of premature failure of concrete structures exposed to the sulphate environment [1]. This happens because the classic sulphate attack tests there are no such factors as, for example, pH variation, wetting-drying cycles or freezing/thawing, which accompany the corrosion of concrete during exploitation [1, 2]. The lower temperature slowed down the diffusion of sulphate ions, which led to the slowing of sulphate attack
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